1. Field of the Invention
This invention generally relates to projection display apparatus, and more particularly to a projection display apparatus with two reflective light panels each having a color filter embedded therein.
2. Description of the Related Art
In a projection display system, a liquid crystal display (LCD) panel is used as a modulator for modulating light from a light source so that a projection lens can project the modulated light onto a display screen to form an image. The LCD panel used in such a projection display system mainly includes two types, i.e. a transmissive type and a reflective type.
A reflective type of LCD panel known as a liquid crystal on silicon (LCOS) panel recently receives an attention due to its small size and high resolution and arrangement of reflective LCD elements on a silicon backplane. LCoS panels have a number of significant advantages over other types of reflective LCD panels. For example, crystalline silicon can be used to form active matrix elements of the LCoS panels. The silicon backplane can also be used to form the TFT drivers and other functional circuitry, using well-known and efficient semiconductor manufacturing techniques. Moreover, a larger percentage of the active area can be used for processing video information for display.
In an LCoS projection display system, a single-panel projector and a three-panel projector has been used to achieve a full color. To achieve full color using a white light source, color management systems are needed for partitioning the spectrum into red, green, and blue, either temporally or spatially. In temporal or time sequential color management systems, only a single LCoS panel is needed for producing a full color by sequential colors. In spatial or multi-path color management systems, three LCoS panels are needed and respectively used for each of the primary colors.
For the single-panel systems, overall system cost and size can be small but there exists a color break-up problem. For the three-panel systems, the optical architecture can easily deliver the high lumen output required for large area projection displays but is complex. Therefore, a two-panel system is used so as to overcome the disadvantages in above-mentioned systems. In addition, the two-panel system incorporates the attractive aspects of above-mentioned systems, including high optical throughput and a small size and cost close to these of the single-panel system.
Referring to FIG. 1, it shows a schematic view of a conventional projection display apparatus 100. The projection display apparatus 100 comprises a white light source 102 configured to supply light 103, a first clean-up polarizer. 104, a color switch 106, a polarizating beam splitter 108, a reflective panel 110, and a projection lens 112. The color switch 106 is an electronically switchable spectral filter for generating a red, green, and blue color light 114 sequentially. The polarizating beam splitter 108 receives the single color light 114 and then reflects the single color light 114 to the reflective panel 110. The reflective panel 110 modulates the single color light 114 for changing the polarity of the single light 114 and reflects the modulated single color light 114 so as to pass through the polarizating beam splitter 108. The projection lens 112 receives the modulated single color light 114 from the polarizating beam splitter 108 and then projects the modulated single color light 114.
However, the aforementioned projection display apparatus 100 must project red, green, blue colors sequentially so as to form a full color image: Therefore, the circuit designs are complicated and synchronization is difficult between the color switch 106 and the reflective panel 114. Besides, the use of the color switch 106 and its related circuits increase the overall cost of the projection display apparatus 100.
Accordingly, the present invention provides a novel two-panel projection display apparatus having simple controlled circuits and lower manufacturing cost.